Field of the Invention
The present invention relates to a disk-shaped workpiece dividing method of cutting a disk-shaped workpiece such as a wafer along a plurality of crossing division lines by using a cutting blade to thereby divide the workpiece into individual chips.
Description of the Related Art
In the field of precision parts manufacture, there is a case that a disk-shaped workpiece such as a semiconductor wafer, optical device wafer, glass substrate, and ceramic substrate is divided into a plurality of rectangular chips as a workpiece. In dividing such a workpiece, one side of the workpiece is usually attached to a dicing tape, and a cutting blade is rotated to cut into the workpiece from the other side thereof to the dicing tape. In this condition, the cutting blade being rotated is relatively moved along a division line to fully cut the workpiece over the thickness thereof.
In relatively moving the cutting blade being rotated along the division line, so-called down cut is generally performed in such a manner that the front edge of the cutting blade in the feeding direction thereof cuts into the workpiece from the upper surface toward the lower surface thereof. This is due to the fact that the size of chipping in cutting the workpiece can be suppressed as compared with so-called up cut such that the cutting blade is rotated to cut into the workpiece from the lower surface toward the upper surface thereof. Further, a cutting fluid is supplied to the workpiece, so as to reduce the processing heat generated from the cutting blade during cutting.
In cutting the workpiece along a plurality of crossing division lines set on the workpiece to divide the workpiece into rectangular chips, a plurality of triangular or trapezoidal waste chips are produced near the outer circumference of the workpiece. Each waste chip is smaller in area than each rectangular chip obtained by dividing the workpiece. In the case of a semiconductor wafer and an optical device wafer, the outer circumference of the workpiece is chamfered to form an arc as viewed in a thickness direction of the workpiece, so that an adhesive force of each waste chip to the dicing tape is weak. For these reasons, there is a possibility of chip scattering such that the waste chips may be separated to scatter from the dicing tape during cutting.
On the other hand, the cutting fluid supplied to the cutting blade sticks to the cutting blade and rotates therewith. Accordingly, in the case of the down cut mentioned above, the cutting fluid flows on the workpiece from the front side toward the back side in the feeding direction of the cutting blade. The chip scattering of waste chips mentioned above is increased in risk of occurrence by a phenomenon such that the cutting fluid rotating with the cutting blade may collide with the waste chips. In particular, when the waste chips are formed on the front side in the feeding direction to cause the chip scattering, the waste chips scatter toward the back side in the feeding direction with the flow of the cutting fluid and then fall onto the upper surface of the workpiece. As a result, there arises a problem such that the upper surface of the workpiece may be scratched by the waste chips. To cope with this problem, there has been proposed a dicing tape having a configuration such that an annular portion corresponding to the outer peripheral portion of the workpiece has a large adhesive strength to reduce the chip scattering of the waste chips (Japanese Patent Laid-open No. 2013-21109).